To do this we consider the degree of causal relevance <math>(cr)</math> of an event <math>E_1</math> with respect to an event <math>E_2</math> where:
To do this we consider the degree of causal relevance ( c r ) {\displaystyle (cr)} of an event E 1 {\displaystyle E_{1}} with respect to an event E 2 {\displaystyle E_{2}} where: